I'm not an "expert", but I did stay at a Holiday Inn Express last night.

I've brewed 5 or 6 all-grain batches in my basement with propane with just one small window open and a relatively small vent fan (and a CO monitor about 3 feet from the burner). My last two I also put a fan in the window to push more air out but my first 4 batches I didn't do that and had no problems.

It's probably more propane being burned, but I justified this procedure to myself thinking about people who use gas ovens for hours at a time with less ventilation and don't die, so I'm pretty sure I will be OK as well.

Great news.....Thanks for the input, I certainly appreciate all of the comments from brewers who have been brewing with gas in their basements.

Well, brew day went off without a hitch.....Total time from adding water to pots to complete cleanup, 5-1/2 hours. I had a lot of distractions though (buddies over to "help") and it was the first time with this setup. The burners were freaking AMAZING!!! It will take me a few times to get into a groove and I found a few things I need to add...nothing major, just some nice add-ons that will make things more efficient and help keep certain things closer at hand, and such. But as far as the gas and venting goes, all is good....I AM STILL ALIVE, to all of you "death will come to all basement gas brewers" electric brewers, IT CAN BE DONE, SAFELY...

I was advised that there was absolutely NO odor throughout the rest of the house, only outside in the back yard where the vent exits the house.
:-)

I did however forget to take a gravity reading.....(frustrating). I only have a pre-boil reading. Oh well. Fermenting is strong already so I am not worried about it.

I will keep y'all posted on anything I can think of regarding this basement gas set-up. I am sure I will think of something and I am sure as the weather turns warmer I will have new problems to face.

Just for the hell of it.....and because i am bored, here's a pic of the beer's final resting place. I am so glad I did all of these builds to "save" money. I will probably break even in about 17 years.

Update: Three successful batches so far and have my brew day/"system" down already. Hit my gravity of 1.060 dead on the money on yesterday's batch. Still no issues with CO or the likes. Built a counter-flow chiller as my latest bell and whistle. Highly recommend it if you don't currently use one. Used a suggestion from a friend and followed the steps on a Youtube video for the build of the chiller. If you have been thinking about doing it, bite the bullet and just do it. You will not regret it, I promise.

I forgot to add that when I made this stand I installed some "L" shaped angle steel for the full length to keep the flame/pots off the perforated angle iron and the iron still looks perfect (not faded and "crispy") unlike some similar stands. It was fairly cheap, simple to add on, and acts as a very good burner grate.

One more quick suggestion for a very cost effective pump cover.....I just took a piece of 4" duct and cut it to fit the full length of the pump with a couple inches of overhang and then squeezed it to about 3" to create some tension then just slipped it over the pump. It holds on tight, it has not moved at all and most importantly it keeps the pumps dry.